1. Field of the Invention
This invention relates to a process for the adsorptive separation of cyclohexene from a mixture containing as main components benzene, cyclohexene and cyclohexane.
2. Description of the Prior Art
A mixture containing as main components benzene, cyclohexene and cyclohexane is ordinarily obtained as a reaction product in the process for preparing cyclohexene, for example, by selective hydrogenation of benzene, selective dehydrogenation of cyclohexane or oxidative dehydrogenation of cyclohexane.
Cyclohexene is a starting material for use in the synthsis of organic compounds such as cyclohexanol and adipic acid. In order to obtain cyclohexene from the above-mentioned mixture advantageously on an industrial scale, the separating and purifying operation of the reaction mixture is very important. There have been proposed various processes for separating cyclohexene from the above-mentioned reaction mixture.
For example, there has been proposed a method comprising passing the reaction mixture through a specially treated cation exchange resin to separate the mixture into the respective components. According to this process, the intended separation can be attained by simple procedures. This process, however, is still not satisfactory in that dissolution of the ion exchange resin into the mixture takes place, deterioration of the ion exchange resin occurs, the purity of the separated product is low and a purification step becomes necessary for enhancing the purity, with the result that the process becomes complicated.
We made researches with a view to overcoming these defects of the above-mentioned conventional process, and we found that when cyclohexene is separated and recovered from a mixture containing benzene and/or cyclohexane and cyclohexene, if a type X aluminosilicate zeolite capable of selectively adsorbing benzene and/or cyclohexene is used as an adsorbent, cyclohexene of a high purity can be separated simply and relatively advantageously. We have already proposed this process (see Japanese Laid-open Patent Application No. 41,844/79).
When cyclohexene is separated from a ternary mixture containing benzene, cyclohexene and cyclohexane according to the above-mentioned process, this separation must be carried out by the following two sequential separating steps: (1) the step of removing benzene from the mixture by selective adsorption and (2) the step of separating cyclohexene from the remaining binary mixture comprising cyclohexene and cyclohexane by selective adsorption. This is because these three components tend to be adsorbed on the above adsorbent in the order of benzene, cyclohexene and then, cyclohexane.